The bar graphs in the profit/loss graph divide the period into discrete sub-periods, e.g. in a "Monthly" view, the bars are per week. If the first bar does not align well with the start of the period, then the scale is not shown on the vertical axis.
For example, see December 2012 (1st December is a Saturday), where the first week/bar ends overlaps the axis, so the scale is lost.
Compare this to October 2012 (1st October is a Monday), where the first week/bar starts after the axis, and so the scale is visible
From a quick sample of months in 2012, the only time you see the scale is when the month starts on a Monday.
See attached screenshot for an example. The screenshot is of the graph from a monthly view of December 2012, and extends all the way to the edge of the window.
You're right, thanks for pointing it out. It must be a result of my recent chart drawing upgrades with the automatic X-axis adjustments that take place when weekly bars overflow. I seldom use date range smaller than a year, that's probably why I missed it.
(from [13518b6a6adc]) [#352 state:fixed] Fixed glitch in bar graph's xaxis drawing.